OxiRS Rule Engine

Status: Beta Release (v0.1.0-beta.1) - Released November 16, 2025

✨ Beta Software: Production-ready with API stability guarantees and comprehensive testing.

A high-performance, comprehensive reasoning engine for Semantic Web applications, implementing forward chaining, backward chaining, RETE networks, RDFS, OWL RL, and SWRL rule processing.

Features

🚀 Core Reasoning Engines

• Forward Chaining - Efficient data-driven inference with pattern matching and built-in predicates
• Backward Chaining - Goal-driven proof search with cycle detection and caching
• RETE Network - High-performance pattern matching for real-time rule execution

🎯 Standards Compliance

• RDFS Reasoning - Complete RDFS entailment rules (rdfs2, rdfs3, rdfs5, rdfs7, rdfs9, rdfs11)
• OWL RL Support - Class/property equivalence, characteristics, identity reasoning
• SWRL Integration - Semantic Web Rule Language with extensive built-in predicates

⚡ Performance Features

• Incremental Updates - Efficient handling of dynamic knowledge base changes
• Pattern Indexing - Optimized rule and fact lookup with caching
• Memory Optimization - Efficient data structures for large-scale reasoning
• Statistics & Monitoring - Comprehensive performance metrics and tracing

Installation

Add to your Cargo.toml:

# Experimental feature
[dependencies]
oxirs-rule = "0.1.0-beta.1"

Quick Start

use oxirs_rule::*;

// Create a new rule engine
let mut engine = RuleEngine::new();

// Add facts
engine.add_fact(atom!(
    "knows", 
    term!("alice"), 
    term!("bob")
));

// Add rules
engine.add_rule(rule!(
    [atom!("knows", var!("X"), var!("Y"))],
    [atom!("friend", var!("X"), var!("Y"))]
));

// Perform forward chaining inference
let stats = engine.forward_chain()?;
println!("Derived {} new facts", stats.facts_derived);

// Query the knowledge base
let results = engine.query(&atom!("friend", var!("X"), var!("Y")))?;
for result in results {
    println!("Friend relationship: {:?}", result);
}

Architecture

Core Components

• RuleEngine - Main interface unifying all reasoning strategies
• ForwardChainEngine - Data-driven inference with fixpoint calculation
• BackwardChainEngine - Goal-driven proof search with memoization
• ReteNetwork - High-performance pattern matching network
• RdfsReasoner - RDFS schema reasoning and entailment
• OwlReasoner - OWL RL profile reasoning
• SwrlEngine - SWRL rule processing with built-in functions

Data Structures

// Core data types
pub struct Rule {
    pub head: Vec<RuleAtom>,
    pub body: Vec<RuleAtom>,
}

pub struct RuleAtom {
    pub predicate: String,
    pub terms: Vec<Term>,
}

pub enum Term {
    Variable(String),
    Constant(String),
    Literal(String),
}

Reasoning Strategies

Forward Chaining

Ideal for:

• Batch processing of large datasets
• Materializing all possible inferences
• Data integration and ETL processes

let stats = engine.forward_chain()?;
println!("Facts derived: {}", stats.facts_derived);
println!("Rules fired: {}", stats.rules_fired);

Backward Chaining

Ideal for:

• Query-driven reasoning
• Interactive applications
• Proof explanation and validation

let goal = atom!("ancestor", term!("alice"), var!("X"));
let proofs = engine.backward_chain(&goal)?;
for proof in proofs {
    println!("Proof path: {:?}", proof.derivation_path);
}

RETE Network

Ideal for:

• Real-time rule processing
• Incremental updates
• High-throughput applications

let mut rete = ReteNetwork::new();
rete.add_rule(&rule);
rete.add_fact(&fact);
let results = rete.execute()?;

Built-in Predicates

Comparison Operations

• equal(?x, ?y) - Equality testing
• notEqual(?x, ?y) - Inequality testing
• lessThan(?x, ?y) - Numeric comparison
• greaterThan(?x, ?y) - Numeric comparison

Mathematical Operations

• add(?x, ?y, ?result) - Addition
• subtract(?x, ?y, ?result) - Subtraction
• multiply(?x, ?y, ?result) - Multiplication

String Operations

• stringConcat(?s1, ?s2, ?result) - String concatenation
• stringLength(?string, ?length) - String length

Utility Predicates

• bound(?var) - Variable binding check
• unbound(?var) - Variable unbound check

RDFS Reasoning

Automatic inference of:

• Class hierarchies (rdfs:subClassOf)
• Property hierarchies (rdfs:subPropertyOf)
• Domain and range constraints (rdfs:domain, rdfs:range)
• Type membership (rdf:type)

let mut rdfs = RdfsReasoner::new();
rdfs.add_schema_triple("Person", "rdfs:subClassOf", "Agent");
rdfs.add_data_triple("alice", "rdf:type", "Person");

let inferred = rdfs.materialize()?;
// Automatically infers: alice rdf:type Agent

OWL RL Reasoning

Support for:

• Property characteristics (functional, transitive, symmetric)
• Class equivalence and disjointness
• Individual identity (owl:sameAs, owl:differentFrom)
• Basic property restrictions

let mut owl = OwlReasoner::new();
owl.add_axiom("hasParent", "rdf:type", "owl:TransitiveProperty");
owl.add_fact("alice", "hasParent", "bob");
owl.add_fact("bob", "hasParent", "charlie");

let inferred = owl.reason()?;
// Automatically infers: alice hasParent charlie

SWRL Rules

Support for complex rule definitions:

// Person(?p) ∧ hasAge(?p, ?age) ∧ greaterThan(?age, 18) → Adult(?p)
let swrl_rule = SwrlRule {
    body: vec![
        SwrlAtom::Class("Person".to_string(), SwrlArgument::Variable("p".to_string())),
        SwrlAtom::DataProperty("hasAge".to_string(), 
            SwrlArgument::Variable("p".to_string()), 
            SwrlArgument::Variable("age".to_string())),
        SwrlAtom::BuiltIn("greaterThan".to_string(), vec![
            SwrlArgument::Variable("age".to_string()),
            SwrlArgument::Literal("18".to_string())
        ])
    ],
    head: vec![
        SwrlAtom::Class("Adult".to_string(), SwrlArgument::Variable("p".to_string()))
    ]
};

Performance Characteristics

Scalability

• Forward Chaining: O(n³) worst case, optimized for sparse rules
• Backward Chaining: O(2^n) worst case, pruned with cycle detection
• RETE Network: O(1) for fact insertion, O(n) for rule addition

Memory Usage

• Efficient fact storage with deduplication
• Rule indexing for fast pattern matching
• Configurable caching strategies

Benchmarks

• 1M+ triples: <60 seconds for full materialization
• 10K+ rules: <10 seconds for compilation
• Memory usage: <8GB for 1M triple datasets

Integration

With oxirs-core

use oxirs_core::model::{Triple, IRI};
use oxirs_rule::RuleEngine;

let mut engine = RuleEngine::new();
// Convert oxirs-core triples to rule facts
engine.add_triple(&triple)?;

With SPARQL

// Use reasoning results in SPARQL queries
let inferred_facts = engine.get_materialized_facts();
// Add to SPARQL dataset for querying

Testing

Run the comprehensive test suite:

# Run all tests
cargo nextest run --no-fail-fast

# Run specific reasoning tests
cargo nextest run -p oxirs-rule --no-fail-fast

# Run performance benchmarks
cargo test --release --features benchmarks

Test Coverage

• 34/34 tests passing (100% success rate)
• Unit tests for all reasoning algorithms
• Integration tests with real-world datasets
• Performance regression tests

Configuration

use oxirs_rule::config::EngineConfig;

let config = EngineConfig {
    max_iterations: 1000,
    cache_size: 10000,
    enable_statistics: true,
    reasoning_strategy: ReasoningStrategy::Hybrid,
};

let engine = RuleEngine::with_config(config);

Error Handling

Comprehensive error types with detailed context:

use oxirs_rule::error::RuleEngineError;

match engine.forward_chain() {
    Ok(stats) => println!("Success: {} facts derived", stats.facts_derived),
    Err(RuleEngineError::UnificationError(msg)) => {
        eprintln!("Unification failed: {}", msg);
    },
    Err(RuleEngineError::CycleDetected(path)) => {
        eprintln!("Infinite recursion detected: {:?}", path);
    },
    Err(e) => eprintln!("Other error: {}", e),
}

Logging and Monitoring

Built-in tracing support:

use tracing::{info, debug};

// Enable tracing
tracing_subscriber::init();

// Reasoning operations automatically logged
let stats = engine.forward_chain()?;
// Logs: "Forward chaining completed: 1000 facts derived, 50 rules fired"

Contributing

1. Follow Rust 2021 edition best practices
2. Maintain >95% test coverage
3. Use cargo clippy and cargo fmt
4. Add comprehensive documentation
5. Include performance benchmarks

License

Licensed under the Apache License, Version 2.0 or the MIT License, at your option.

Status

🚀 Beta Release (v0.1.0-beta.1) – November 16, 2025

Highlights:

• ✅ Forward/backward chaining over persisted datasets with automatic inference snapshots
• ✅ RETE network optimized with SciRS2 metrics and tracing hooks
• ✅ Integrated with federation-aware SPARQL workflows for rule-driven post-processing
• ✅ 89/89 tests passing plus CLI end-to-end coverage
• 🚧 Advanced distributed reasoning (planned for beta)